The invention concerns a switchable support element for a finger lever of a valve train of an internal combustion engine, said support element being installed in a cylinder head of an internal combustion engine and comprising an outer housing, an inner element, a slide and a housing for the slide, said outer housing being installed in a reception of the cylinder head and receiving the inner element for axial displacement, a bore provided in the inner element and a bore provided in the outer housing being aligned to each other in a relative axial position, the slide being at least partially displaceable out of the housing into said bores for coupling the inner element to the outer housing, and the housing being seated in the cylinder head with an inner end adjacent the bore of the outer housing.
A support element of the pre-cited type considered to be generic is known from DE 44 22 340 A1. This support element is likewise switchable but for the purpose of coupling, it is intersected axially beneath its clearance compensation element by a slide. At its end facing away from the support element, the slide extends in a separate housing in the cylinder head. To effect coupling, an end of the slide extends fully through the support element. This document further discloses a so-called lost motion spring that acts on an inner element of the support element axially beneath the slide.
A drawback of the aforesaid support element is that it has a relatively large design height. It must be noted that the clearance compensation element with the slide and the lost motion spring are stacked one on top of the other. Design space problems can arise from the fact that the support element intersects cooling water or gas exchange canals or the like that may be located in this region. It is further noted that the support element cannot be supplied together with the housing for the slide because these are separate components. Due to the separate mounting of the housing for the slide in the cylinder head, misalignments between the slide and the bores provided in the support element for coupling purposes can also occur.
The object of the invention is therefore to provide a switchable support element of the pre-cited type in which the mentioned drawbacks are eliminated.
The invention achieves this object by the fact that the inner end of the housing comprises an annular extension that is installed in the bore of the outer housing, or that the inner end of the housing is connected to the outer housing by a flange, and the slide is adapted to be operated electromagnetically while being configured as an actuator rod with an armature plate.
In an alternative solution, this object is achieved by a hydraulically displaceable slide and by the fact that the inner end of the housing comprises an annular extension that is installed in the bore of the outer housing, or that the inner end of the housing is connected to the outer housing by a flange.
In a particularly preferred embodiment according to one of the dependent claims, the bores of the inner element and the outer housing extend in radial direction, and the bore of the inner element is made as a pocket bore.
In this way, a support element is created in which the initially cited drawbacks are eliminated. Essentially, this support element does not require more design space than non-switchable support elements so that it can be easily adapted to cylinder heads of conventional design, or, to put it differently, the support element has a shorter length than switchable prior art solutions. This is accomplished on the one hand by the fact that the hitherto used stacked construction is avoided by configuring the bore in the inner element as a pocket bore.
On the other hand, a simple form of loading the slide through means arranged laterally in the cylinder head is provided. If required, the slide and the housing can be supplied together with the switchable support element because the housing can be connected in advance to the outer housing through its annular extension. All that is then required is to provide a longitudinal recess at a suitable location in the cylinder head for inserting the housing. However, it is also conceivable to have a separate housing and insert it laterally into the cylinder head and connect it to the outer housing through its annular extension.
Due to the preferred press fit between the annular extension and the outer housing the possible prior art alignment errors between the housing, and thus between the slide and the bores in the support element are effectively avoided.
Advantageously, according to a further embodiment of the invention, a hydraulic clearance compensation element, known per se, is installed in the support element. Thus, mechanical or hydraulic clearance adjusting measures at other locations in the valve drive can be dispensed with.
Further dependent claims relate to alternative modes of operating the slide. For example, this can be loaded electromagnetically in at least one direction of displacement. However, it is also conceivable to load the slide electromagnetically in both its directions of displacement. For this, the slide comprises an armature plate that may be formed integrally therewith and likewise extend in the housing.
For the electromagnetic or hydraulic displacement of the slide in at least one direction, pressurelessly locked or unlocked configurations, such as are known per se in the technical field, are also conceivable.
If, as alternatively proposed, the slide is displaced hydraulically in at least one direction of displacement, it may be displaced in the opposite direction by the force of a spring means such as at least one compression spring or also by a hydraulic medium. Appropriately, the hydraulic medium is routed out of the cylinder head adjacent the housing into a pressure chamber situated in front of a pressure plate of the slide.
It is both conceivable and provided for by the invention to make the annular extension of the housing as a separate component. This can be of advantage from the fabrication and assembly point of view. A simple way of connecting the annular extension to the housing is to make a snap connection using a locking ring. But a force-locked or positive engagement is also conceivable for this purpose.
In place of the aforesaid press fit between the annular extension and the outer housing, it can also be advantageous to connect the housing to the outer housing through a flange.